Parasitic nematodes in the genus Trichinella are commonly found in endothermic (warm-blooded) animals. The most common species, Trichinella spiralis, is found in many species of mammals. The infective larvae live in specialised capsules call "nurse cells" (which are muscle cells which have been heavily modified by the parasite), and they are transmitted into different mammalian host via carnivory or scavenging on carcasses. Trichinella zimbabwensis deviates somewhat from this pattern. While it is still transmitted to a new host via the ingestion of infected muscle tissue, unlike T. spiralis, it does not encapsulate and it is also found in reptilian hosts, specifically crocodiles. However, it does not occur exlusively in reptiles and can also infect mammals. Given that it is able to survive in both ectothermic and endothermic hosts, while other species of Trichinella can only survive in endothermic hosts in the wild, this raises intriguing questions about the evolutionary origin of the genus Trichinella.
For more details, see:
Pozio, E. et al. (2002) Trichinella zimbabwensis n.sp. (Nematoda), a new non-encapsulated species from crocodiles (Crocodylus niloticus) in Zimbabwe also infecting mammals. International Journal for Parasitology 32:1787-1799.
Contributed by Tommy Leung.